The present invention relates to the manufacture of cigarette rods; and in particular to the manufacture of cigarette rods of controlled density and firmness, and having very low amounts of hard spots, soft spots and loose ends.
Cigarettes are popular smoking articles which have a substantially cylindrical rod shaped structure and include a charge of smokable material (e.g., tobacco in cut filler form) surrounded by a paper wrapper thereby forming a tobacco rod or cigarette rod. Some cigarettes have cylindrical filters aligned in an end-to-end relationship with the tobacco rod. Typically, filters are manufactured from fibrous materials such as cellulose acetate and are attached to the tobacco rod using a circumscribing tipping material.
Popular cigarettes include blends of tobacco materials as well as blends of tobacco materials with certain amounts of tobacco substitute materials. For example, cigarettes often include blends of flue-cured, Burley and Oriental tobaccos; cut rolled tobacco stems, reconstituted tobacco materials; and volume expanded tobacco materials. Recently, however, cigarette manufacturers have been expending efforts towards providing certain cigarette products having smokable blends having high filling capacities. Typically, blends which have high filling capacities comprise relatively high levels of volume expanded smokable filler materials.
During the cigarette manufacturing process, several inspections for quality are performed. Such inspections include checks for loose ends, hard spots and soft spots. If a particular cigarette rod is not within a tolerance range set by the manufacturer, the rod is rejected. Recently, cigarette manufacturers have desired to produce cigarettes at very high rates, to produce cigarettes using high filling capacity blends, and to produce cigarettes using high amounts of volume expanded tobaccos. These factors have made it increasingly difficult to produce consistent quality cigarette rods having controlled integrity. As a result, either relatively high amounts of cigarette rods are rejected for not being within the tolerance range set by the manufacturer, or cigarettes of inconsistent integrity (and hence low quality) are produced. As a consequence, a cigarette manufacturer desiring both high quality control and a low amount of rejected cigarettes often is forced to manufacture cigarettes having relatively high levels of volume expanded smokable filler at low speeds (e.g., so as to manufacture less than about 4,000 cigarettes per minute in certain circumstances).
During the manufacture of cigarette rods, a stream of smokable filler is compressed using at least one constriction member. One of the constriction members commonly is known in the art as a tongue, a compression foot or a compacting finger. Another constriction member commonly is referred to as a scrape, shoe or short tongue. As such, the filler stream is compressed toward the center of a web of wrapping material to assist in forming the stream into a cylinder about which the web is wrapped. The majority of the compression of the filler is provided by the tongue. Should the cigarette making machine be running at a high rate of speed or the stream of filler contain a relatively high amount of volume expanded tobacco, there is a tendency for the filler to accumulate and release in an uncontrolled manner in the tongue region of the cigarette making machine because of the frictional forces which occur in the tongue region. Such an undesirable tendency of the filler to accumulate and release is increased as the speed at which the continuous cigarette rod is manufactured increases. As a consequence, a continuous rod having inconsistent amounts of filler along the length thereof will result. Such a rod of inconsistent quality will result in a large number of rejected cigarettes or cigarettes of poor consistent quality.
It has been proposed to deliver compressed air through a passageway of the tongue as a method for reducing the contact of the stream of filler with the tongue. However, such a method is not entirely effective in providing cigarette rods of consistent uniformity and high quality.
Various references propose introducing certain substances through the tongue during cigarette rod manufacture. For example, U.S. Pat. No. 4,186,754 to Labbe proposes feeding water or alcohol to the surface of the tongue which contacts the stream of a particular type of tobacco in order to dilute and reduce the viscosity of gum which reportedly builds up on the tongue. U.S. Pat. No. 4,409,995 to Nichols proposes applying flavorant in particulate or liquid form to a cigarette rod through the tongue region of a cigarette making machine. U.S. Pat. No. 4,619,276 to Albertson et al proposes applying flavorant in foam form to a cigarette rod through the tongue region of a cigarette making machine. However, the references address neither the high speed manufacture of cigarette rods nor the manufacture of cigarette rods having relatively high amounts of volume expanded smokable filler material.
It would be highly desirable to provide a process for manufacturing cigarette rods of highly consistent quality at high speeds.